RESEARCH by Cardiff University experts will today end the debate about whether ADHD is a real disorder or simply an excuse for bad behaviour.

A team has discovered the first direct genetic link to the condition, which is thought to affect about one in 50 children in the UK. It is hoped the discovery will lead to a better understanding of ADHD – attention deficit hyperactivity disorder – and pave the way to new treatments.

Professor Anita Thapar, professor of child and adolescent psychology at Cardiff University, who led the study, said: “We hope these findings will help overcome the stigma associated with ADHD. Too often people dismiss ADHD as being down to bad parenting or poor diet. As a clinician, it was clear to me that this was unlikely to be the case. Now we can say with confidence that ADHD is a genetic disease and that the brains of children with this condition develop differently to those of other children.”

The research, which involved analysing the genomes of 336 children and is published today in The Lancet, found genetic variations – subtle “chunks” of missing or extra DNA – on the 16th chromosome. These segments are known as copy number variants (CNVs).

Dr Kate Langley, from Cardiff University’s school of medicine, said: “ADHD is not caused by a single genetic change, but is likely caused by a number of genetic changes, including CNVs, interacting with a child’s environment.

“Screening children for the CNVs that we have identified will not help diagnose their condition. We already have very rigorous clinical assessments to do just that.”

The research also found significant overlap between these CNVs and the genetic variants implicated in autism and schizophrenia. The team said this provides strong evidence that ADHD is a neuro-developmental disorder, which means the brains of children with the disorder differ from those of other children.

Prof Thapar said: “ADHD is clinically quite distinct from autism and schizophrenia but there appears to be a shared biology between the conditions, which is not uncommon in medicine.”

And Dr Nigel Williams, a senior lecturer from Cardiff University’s department of psychological medicine who took part in the study, said: “Children with ADHD have a significantly higher rate of missing or duplicated DNA segments compared to other children and we have seen a clear genetic link between these segments and other brain disorders. These findings give us tantalising clues to the changes that can lead to ADHD.”

The research was funded by the Wellcome Trust, with additional support from Action Medical Research, the Baily Thomas Charitable Trust, the Medical Research Council and the European Union.